We have an older model stihl that we use at my grandfathers farm for 15+ years now. Still running good.Only thing we ever did to it was a diaphram and spark plug about 5 years ago.I have a 3yr old stihl trimmer that i bought brand new and havn't had any issues.The only chainsaws we buy anymore are the stihl.They never quit on us yet.I think we are on our 3rd farm boss chain saw now.We use them hard for 10 yrs and trade them in.The one we had before the latest one we have my brother gave my grandfather the trade in value so he had one for his house.Still going strong.I'm sure there is other brands that run well but we had good luck with the stihl brand and stuck with it ever since.This is just my experience.

As others have said, Ethanol in the gasoline is really rough on small internal combustion engines....2 cycle or 4 cycle....doesn't matter!

I think one problem with 2 cycle engines is the fuel mixtire. You have to get the mixture EXACTLLY the same each and every time or your engine will not run the same as it did the previous time.

I'm sure most everyone here has heard of or even uses a fuel stabilizer. I know this will probably open up a can of worms, but I have used several brands over the years, and I feel the best (in my opinion) stabilizer and fuel system cleaner is SEAFOAM. I have had very good results with this product, and will continue to use it in the fuel for my mowers, GT's, chainsaws, weedeater, and motorcycles. In the late fall I will add the SEAFOAM to a 5 gallon container of gasoline then use this fuel for all my small engines through thre fall and winter. This is another problem with Ethanol....it has a very short shelf life and causes the fuel to draw moisture. This is the reason we have to add a stabilizer to our fuel.

The golf courses I worked at have used the pro model Stihls for the past 15 or so years and never had an engine seize up (except one that was ran with straight gas) and they were usually ran over 25 hours a week and at least 30 weeks a year. I used AMS Oil 50:1 Interceptor 2 cycle oil mixed at 50 gallons of premium no-lead to a gallon of the oil in a 55 gallon drum. I did all the mixing and the 2 cycle cans were well marked. We normally got five years out of a machine, they were serviced once a month and tore down during the winter for decarbonizing the cylinder.

At home I used an older Echo straight shaft and the same oil and gas up to this year when one of the two BP stations in town started selling "recreational gas" which is supposed to be ethanol free 91 octane gas for the same price as the 91 octane 10% ethanol premium. Hopefully that will help with the diaphragms and gaskets that stretch out of shape with the alcohol. I use the new gas in everything except my wife's van and my truck. Most of the 2 cycles that come in the shop have mufflers that are full of carbon and carb gaskets and diaphragms that are shot.

The golf courses I worked at have used the pro model Stihls for the past 15 or so years and never had an engine seize up (except one that was ran with straight gas) and they were usually ran over 25 hours a week and at least 30 weeks a year. I used AMS Oil 50:1 Interceptor 2 cycle oil mixed at 50 gallons of premium no-lead to a gallon of the oil in a 55 gallon drum. I did all the mixing and the 2 cycle cans were well marked. We normally got five years out of a machine, they were serviced once a month and tore down during the winter for decarbonizing the cylinder.

At home I used an older Echo straight shaft and the same oil and gas up to this year when one of the two BP stations in town started selling "recreational gas" which is supposed to be ethanol free 91 octane gas for the same price as the 91 octane 10% ethanol premium. Hopefully that will help with the diaphragms and gaskets that stretch out of shape with the alcohol. I use the new gas in everything except my wife's van and my truck. Most of the 2 cycles that come in the shop have mufflers that are full of carbon and carb gaskets and diaphragms that are shot.

I burn the carbon out of the mufflers by mounting them in a vice on one of the rolled edges and then carefully heating them to red hot with an oxy-acetylene torch. I continue to heat them until the flame coming out of the muffler dies down and the smoke stops rolling out. Let it cool and then put it back on. This is done once a year on all of them and during the season if the engine exhaust flow falls off. This can also be done with a propane or MEPP torch but will take longer.

We use Amsoil Saber Pro and unfortunately ethenol gas at the resort. I have the Techs close the plug gap just slightly from spec for a bit of a hotter burn and we rarely have carbon issues. Very precise mixture as well and only the Techs do the mixing. Always 64 ounces to 25 gallons.

Once I pulled the old fuel line out, I found a split on the tank side. Went to town & picked up a foot of new line, and back in business, running fine! I got a bit aggravated when it started acting up. Should have known it was just a line. But been under a lot of stress and it was awfully hot/humid yesterday when this happened, so I let it get to me.

I think I'm running the oldest string trimmer in this thread LOL! I dug mine out of my FIL's dumpster about 15 years ago. It's an IDC (Inertia Dynamics Corp.) They were bought out by Ryobi in the late '80s. All Ryobi wanted was their shaft design, so the engines are no longer being produced , however, the shaft on it was bent. Luckily the Ryobis of the era were still using the IDC design shaft. I replaced the shaft with yet another one I scrounged out of the garbage on cleanup day. It was probably 10 years old when I got it and the only work I've ever done to it was swap out the shaft that first season I had it and change the spark plug and fuel line. I'm needing to purchase a new filter assembly for the fuel tank, but they're still available and fairly inexpensive (about $5). Just an FYI for everyone. I picked up some TYGON fuel line at one of the local repair shops at the beginning of last season and it has held up fantastically! The cheapy stuff that I was buying at TSC would get me through most of a summer then and have to be replaced.
As a side note, I bought some GT stuff from a guy who used to have a repair shop. As we were haggling through the deal, I spotted a familiar shape on a nearby shelf (A new looking IDC engine and transmission) and asked how much he wanted for it. He said $5 and I almost caught my pocket on fire getting the money out so fast! I now have a good replacement engine for the eventuality when this one finally dies.
I should be good for the rest of my weedwacking career! Oh, and did I mention that it starts on the first or second pull every time! (after the initial start of the season which might take a few more)